The purpose of the present study is: (1) to determine quantitatively whether the carotid sinus baroreceptors undergo adaptive changes (resetting) during the chronic phase of one-kidney and two-kidney Goldblatt renal hypertension; (2) if resetting occurs, then to determine whether these adaptive changes involve mechanical properties of the carotid sinus wall elements or the receptor neural elements; and (3) to determine whether sympathetic efferents to the carotid sinus region modulate the resetting in one or both types of hypertension models. The results obtained should enhance our understanding of the role of baroreceptor function in the pathogenesis of human renovascular hypertension, and should provide further quantitative data for rigorous diagnosis and clinical management of this disease.